MT28F320A18 Micron Technology, MT28F320A18 Datasheet - Page 17

• Manufacturer Part Number: MT28F320A18
• Description: FLASH MEMORY
• Manufacturer: Micron Technology

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DataSheet
BLOCK LOCKING
locking scheme that allows each block to be individu-
ally locked or unlocked with no latency.
blocks. The first level allows software-only control of
block locking (for data that needs to be changed fre-
quently), while the second level requires hardware
interaction before locking can be changed (code that
does not require frequent updates). Control pins WP#,
DQ1, and DQ0 define the state of a block; for example,
state [001] means WP# = 0, DQ1 = 0 and DQ0 = 1.
Table 9 defines all of the possible locking states.
Note:
Locking operation
1. All blocks are locked on power-up. They can then be
2. The LOCK DOWN command locks a block and pre-
Locked State
reset sequence, all blocks are locked (states [001] or
[101]). This means full protection from alteration. Any
PROGRAM or ERASE operations attempted on a
locked block will return an error on bit SR1 of the sta-
tus register. The status of a locked block can be
changed to unlocked or lock down using the appropri-
ate software commands. Writing the lock command
sequence, 60h followed by 01h, can lock an unlocked
block.
Unlocked State
programmed or erased. All unlocked blocks return to
the locked state when the device is reset or powered
down. An unlocked block can be locked or locked
down using the appropriate software command
sequence (see Table 4).
2 Meg x 16, 1.8V Enhanced+ Boot Block Flash Memory
MT28F320A18_F.fm – Rev F 08/03 EN
4
U
The MT28F320A18 Flash memory provides a flexible
The device offers two-level protection for the
The following summarizes the locking operation.
unlocked or locked down with the UNLOCK and
LOCK DOWN commands.
vents it from being unlocked when WP# = 0.
• When WP# = 1, lock down is overridden. Com-
• When WP# returns to 0, locked down blocks
• Lock down is cleared only when the device is
After a power-up sequence completion, or after a
Unlocked blocks (states [000], [100], [110]) can be
.com
mands can then unlock/lock locked down blocks.
return to lock down.
reset or powered down.
All blocks are software-locked upon power-
up sequence completion.
1.8V ENHANCED+ BOOT BLOCK FLASH MEMORY
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17
Locked Down State
tected from PROGRAM and ERASE operations, but
their protection status cannot be changed using soft-
ware commands alone. A locked or unlocked block can
be locked down by writing the lock down command
sequence, 60h followed by 2Fh. Locked down blocks
revert to the locked state when the device is reset or
powered down.
input pin. When WP# = 0, blocks in lock down [011] are
protected from program, erase and lock status
changes. When WP# = 1, the lock down function is dis-
abled ([111]) and locked down blocks can be individu-
ally unlocked by a software command to the [110]
state, where they can be erased and programmed.
These blocks can then be relocked [111] and unlocked
[110] as desired as long as WP# remains HIGH. When
WP# goes LOW, blocks that were previously locked
down return to the locked down state [011] regardless
of any changes made while WP# was HIGH. Device
reset or power-down resets all locked blocks, including
those in lock down, to locked state (see Table 9).
Reading a Block’s Lock Status
read device identification mode. To enter this mode,
write 90h to the device. Subsequent READs at block
address + 00002h will output the lock status of that
block. The lowest two outputs, DQ0 and DQ1, repre-
sent the lock status. DQ0 indicates the block lock/
unlock status and is set by the LOCK command and
cleared by the UNLOCK command. It is also automati-
cally set when entering lock down. DQ1 indicates lock
down status and is set by the LOCK DOWN command.
It can only be cleared by reset or power-down, not by
software. Table 9 shows the locking state transition
scheme.
Locking Operations during Erase
Suspend
ing an ERASE SUSPEND by using the standard locking
command sequences to unlock, lock, or lock down.
This is useful in the case when another block needs to
be updated while an ERASE operation is in progress.
tion, first write the ERASE SUSPEND command (B0h),
then check the status register until it indicates that the
ERASE operation has been suspended. Next, write the
desired lock command sequence to block lock, and the
Blocks that are locked down (state [011]) are pro-
The lock down function is dependent on the WP#
The lock status of every block can be read in the
Changes to block lock status can be performed dur-
To change block locking during an ERASE opera-
2 MEG x 16
©2003 Micron Technology Inc.